Perforation anvil

Abstract

A method and apparatus for perforating a web includes an anvil roll having an outer surface wherein at least a portion of the outer surface defines an anvil surface. The anvil surface includes a plurality of angled grooves having a variable groove width. The method may include phasing the cutting position on the anvil to effect varying perforation patterns.

The invention claimed is: 
     
       1. A method of perforating a web comprising,
 providing a web, 
 passing the web through a nip, wherein the nip is defined as a contact point between a cutting edge and an anvil surface, the cutting edge comprising a portion of a knife roll and the anvil surface comprising a portion of an anvil roll, the anvil roll being adapted to rotate about an anvil roll axis, the knife roll being adapted to rotate about a knife roll axis, the anvil surface comprising a plurality of grooves separated by a plurality of lands, the plurality of grooves being angled and having variable groove widths, 
 perforating the web in the nip at a first machine direction cutting position by pressing the cutting edge against the web and the anvil surface to cut the web at the lands and to maintain the web at the grooves, and 
 phasing the cutting edge relative to the anvil surface to perforate the web at a second machine direction cutting position wherein the grooves have a first width at the first machine direction cutting position and have a different second width at the second machine direction cutting position. 
 
     
     
       2. A method of perforating a web comprising,
 providing a web, 
 passing the web through a nip, wherein the nip is defined as a contact point between a cutting edge and an anvil surface, the cutting edge comprising a portion of a knife roll and the anvil surface comprising a portion of an anvil roll, the anvil roll being adapted to rotate about an anvil roll axis, the knife roll being adapted to rotate about a knife roll axis, the anvil surface comprising a plurality of grooves separated by a plurality of lands, the plurality of grooves being angled and having variable groove widths, and 
 perforating the web in the nip at a first machine direction cutting position by pressing the cutting edge against the web and the anvil surface to cut the web at the lands and to maintain the web at the grooves. 
 
     
     
       3. The method of  claim 2  wherein the web comprises a carrier and a plurality of elastic strands extending in a machine direction and the method further includes perforating the web in a cross-machine direction by cutting or damaging all the strands of elastic and maintaining portions of the carrier as connectors. 
     
     
       4. The method of  claim 3  wherein the elastic strands are aligned over the lands in the nip. 
     
     
       5. An anvil roll comprising an anvil surface wherein the anvil surface includes a plurality of angled grooves having a variable cross-machine direction groove width, wherein the anvil surface is part of an insert and wherein the anvil surface is made of cobalt sub-micron HIP carbide and wherein the grooves have a groove angle of about 25 degrees to 45 degrees. 
     
     
       6. The anvil roll of  claim 5  wherein the anvil surface has a radius in the machine direction of 6 to 12 inches. 
     
     
       7. The anvil roll of  claim 5  wherein the cross-machine direction groove width varies from about 0.015 inches to about 0.006 inches. 
     
     
       8. The anvil roll of  claim 5  wherein the grooves are spaced apart by about 0.1 inches as measured in the machine direction. 
     
     
       9. The anvil roll of  claim 5  wherein the grooves are spaced apart by about 0.160 inches as measured in the cross machine direction. 
     
     
       10. The anvil roll of  claim 5  wherein a majority of the grooves have a straight edge taper. 
     
     
       11. A perforation apparatus comprising,
 a knife roll adapted to be rotated about a knife roll axis, the knife roll comprising at least one cutting edge; 
 an anvil roll adapted to be rotated about an anvil roll axis, the anvil roll axis being parallel with the knife roll axis, the anvil roll having an outer surface wherein at least a portion of the outer surface defines an anvil surface which includes a plurality of angled grooves, wherein a majority of the grooves have a variable groove width, and 
 a cutting nip defined by the point wherein the cutting edge contacts the anvil surface. 
 
     
     
       12. The perforation apparatus of  claim 11  wherein the cutting edge is continuous. 
     
     
       13. The perforation apparatus of  claim 11  wherein the cutting edge is aligned parallel with the knife roll axis. 
     
     
       14. The perforation apparatus of  claim 11  wherein the majority of the grooves have a straight edge taper.